Many of the executives have left or been pushed out as Twitter’s chief executive, Dick Costolo, has brought in a new team to try to increase sluggish user growth at the social network.

But in one very important area of the company — Twitter’s ad business — the leadership has remained relatively untouched.

Adam Bain, Twitter’s global president of revenue and partnerships, has been Twitter’s lead money man since he took the job nearly four years ago. A former executive at Fox Sports Media Group, Mr. Bain came to Twitter to oversee the development of the company’s then nascent advertising products.

In the reorganization after the resignation of Twitter’s No. 2 executive, Ali Rowghani, last month, Mr. Bain also took over control of business development. His role atop the moneymaking machine suggests that he might very well be the second most important person at the company after Mr. Costolo.

Now Twitter frequently runs sponsored video clips, one of the top social media ad products connected to live televised events, and it is rapidly building out its mobile presence, including challenging Facebook’s dominance in mobile app installation ads. This year, Twitter has said, it expects to post $1.2 billion to $1.25 billion in revenue, nearly double the $665 million it took in last year, although the company expects to continue to report net losses.

Along with enlarging the business and courting big advertisers and TV networks, Mr. Bain has poached numerous advertising veterans from technology companies across Silicon Valley to add to his team at Twitter.

Photo

Adam Bain, seen here on the roof of Twitter's San Francisco headquarters in 2012, is the company's head of global revenue and oversees its advertising platform.Credit Noah Berger/Reuters

Google has been a favorite target. Richard Alfonsi left Google in 2012 to lead the efforts to target small- and medium-size businesses, while Shailesh Rao and Stephen McIntyre left Google earlier that year to head Twitter’s Asian and European advertising sales efforts.

Mr. Bain’s top colleague, Kevin Weil, has also risen to prominence. Beginning his career at Twitter as an engineer managing much of the company’s analytics, Mr. Weil quickly moved to the ad side and was promoted three times. He is now vice president for revenue products at the company and is also becoming deeply involved in some nonadvertisement products, such as the hosting and automatic previewing of video clips on the site.

Under Mr. Bain, Twitter has also acquired MoPub and TapCommerce, two start-ups that were in the business of serving advertisements to users of other mobile apps. Even if Twitter’s user growth continues to wane, the thinking goes, the company can still lift its bottom line by selling mobile ads that run in places other than its flagship service.

Ultimately, even if Twitter never adds another user, most analysts expect that Mr. Bain and his team could keep increasing revenue for some time just by showing more and better ads to current users, especially internationally, where very few ads appear in the main feed.

“It depends on whether they want to be a huge company, or just a really profitable company,” said Richard Greenfield, an analyst at BTIG Research.

Correction: July 6, 2014An earlier version of this article misstated Adam Bain's title. He is global president of revenue and partnerships, not vice president. The earlier version also misspelled the given name of the head of Twitter's Asian advertising sales. He is Shailesh Rao, not Shilesh.

A version of this article appears in print on 07/07/2014, on page B5 of the NewYork edition with the headline: With Revenue Roaring, the Twitter Ad Team Is Untouched by Turmoil.